As we become used to being parents of a youngster with Down's syndrome, we learn that our child's thyroid should be checked from time to time. We are told that under-active thyroid (hypothyroidism) is common and not possible to recognise without a blood test because symptoms are similar to aspects of the condition of Down's syndrome itself: lethargy, deep voice, dry skin and overweight.

A blood test is also necessary to identify an over-active thyroid (hyperthyroidism). Although rare in Down's syndrome it is not unknown. Indeed, where it occurs it can be more serious, hence the importance of ensuring children and adults with Down's syndrome are tested. Symptoms can include more frequent visits to the toilet, being over-anxious, poor sleep pattern, fidgetting in bed, enlarged eyes, quicker pulse, weight loss, unclear speech.

Many readers will never need this information but at some time it could be important. Effective treatment of both under-active and over-active thyroid is available as it is to people without Down's syndrome. An endocrinologist explained for a patient with Down's syndrome: a hormone is a chemical made in one place which has its effect elsewhere. Hormones come from glands and control how the body works. Thyroid hormones (particularly thyroxine) control signals, they control the speed of everything in the body. If too much is made (hyperactive) everything goes too fast, if too little (hypoactive) you turn into a snail!